[php]php设计模式 Chain Of Responsibility (职责链模式)

<?php
 2 /**
 3  * 职责链模式
 4  *
 5  * 为解除请求的发送者和接收者之间的耦合,而使用多个对象都用机会处理这个请求,将这些对象连成一条链,并沿着这条链传递该请求,直到有一个对象处理它
 6  *
 7 */
 8 abstractclass Handler
 9 {
10 protected$_handler=null;
11 
12 publicfunction setSuccessor($handler)
13     {
14 $this->_handler =$handler;
15     }
16 
17 abstractfunction handleRequest($request);
18 }
19 
20 class ConcreteHandlerZero extends Handler
21 {
22 publicfunction handleRequest($request)
23     {
24 if($request==0)
25         {
26 echo"0<br/>";
27         } else {
28 $this->_handler->handleRequest($request);
29         }
30     }
31 }
32 
33 class ConcreteHandlerOdd extends Handler
34 {
35 publicfunction handleRequest($request)
36     {
37 if($request%2)
38         {
39 echo$request." is odd<br/>";
40         } else {
41 $this->_handler->handleRequest($request);
42         }
43     }
44 }
45 
46 class ConcreteHandlerEven extends Handler
47 {
48 publicfunction handleRequest($request)
49     {
50 if(!($request%2))
51         {
52 echo$request." is even<br/>";
53         } else {
54 $this->_handler->handleRequest($request);
55         }
56     }
57 }
58 
59 
60 // 实例一下
61 $objZeroHander=new ConcreteHandlerZero();
62 $objEvenHander=new ConcreteHandlerEven();
63 $objOddHander=new ConcreteHandlerOdd();
64 $objZeroHander->setSuccessor($objEvenHander);
65 $objEvenHander->setSuccessor($objOddHander);
66 
67 foreach(array(2,3,4,5,0) as$row)
68 {
69 $objZeroHander->handleRequest($row);
70 }